Crossflow Pros and Cons


We have a mobile cross flow filtration business in the Willamette Valley in Oregon. We use a 2008 Koch machine with hollow fiber cartrdiges which will remove particles to .2 microns. I recently had a winemaker note that he thought the Pinot we filtered took out some of the "greeness" of the tannin profile in his 07 wine. (A vintage known for unripe fruit in some cases.) Is there any science to support this claim, and how does the filtration process affect structure in our Pinots?

Dear Corey:

I encapsulated my views on crossflow clarification in The Crossflow Manifesto in 2001. This is a sequel to The Crossflow Comix which readers may also enjoy as a brief but hilarious history of membranes in the wine industry.

Since then, the practice has become more widespread, and a lot of good winemakers swear by it. If by greenness you mean dry tannin, which is common in pinot, or even the green seed bitterness one often finds in Oregon pinot (and may be an oil), then I think it is possible that crossflow could remove it, which could be a god thing.

The goal of crossflow is to replace DE, which doesn't remove anything except particulates. I've never observed a crossflow that could do this. They remove tannin colloids, which can be a good thing for whites (browning and astringency) and for reds which have coarseness. But my beef is the removal of the fine aroma-integrating colloids which are the heart of the wine.

One thing for sure -- if you crossflow, the run should be completed to the toothpaste stage, so you squeeze out at the end all the structural stuff which gets concentrated in the retentate until it finally passes in the final few gallons of the run. Whether these building blocks can then reorganize into a proper structure is a matter for debate.

Don't look for "science" to be much help on this. Tannin quantification is mired in some very low level political quagmires these days from which it is unlikely to extricate itself for useful investigation any time soon, such as developing an actual language for tannins such as exists in France. You just need to do trials and taste. I'm eager to hear what you're learning.